Method of and apparatus for producing carbon dioxide



May 10, 1938. 3 Hum- AL 2,117,025

METHOD OF AND APPARATUS FOR PRODUCING CARBON DIOXIDE Filed Aug. 24. 1933 4 Sheets- Sheet 1 INVENTORS Fran/r1 in E, Hunt, JafiezHPratt, Heng y 5. Tirre/Z-rfioberll. 721mm;

ATTORNEYS May 10, 1938. F,- B. HUNT Er AL v 2 117,025

METHOD OF AND APPARATUS FOR PRODUCING CARBON DIOXIDE I Filed Aug. 24, 1933 4 Sheets-Sheet 2 INVENTORJ FranklinB.Hunt, Jabez 11. Pratt, HAINJJ Tirrell vfioberl LTumer;

ATTORNEYS May 10, 1938- F, B. HUNT ET AL. 2,117,025

METHOD OF AND APPARATUS 'FOR PRODUCING CARBON DIOXIDE Filed Aug. 24, 1933 4 Sheets-Shee 3 O 8% q 2 a D 1% B (Q P.-

Q a Q Q a R a 1|: O g g: I "a E x F a 3 @1 \Q q INVENTORS Franlrlz'n E. Hunt, Jabez HZ Pratt, Hemgyd. Tirre/Z +Iiabei-Zl. Turner,

ATTORNEYS May 10, 1938. F. B. HUNT Er'AL METHOD OF, AND'A PPARATUS FOR PRODUCING CARBON DIOXIDE Filed Aug. 24. 1933 4 Sheets-Sheet 4 INVENTOR. cjbez H. Pratt, berzl. Turner,

Franklin E. Hunt, Hegy'. T irre 11 +30 ATTORNEYS Patented May 10, 1938 PATENT OFFICE METHOD OF AND APPARATUS FOR PRO- DUCING CARBON DIOXIDE Franklin B. Hunt, Jabez H. Pratt, Henry- S. TirrcIL'and Robert L. Turner, Chicago, 111., assignors to, The Liquid Carbonic Corporation,

Chicago, 111.,

Application August 24,

8 Claims.

The present application relates to a method of and apparatus for producing carbon dioxide, and. more particularly to a novel method and apparatus whereby carbon dioxide may be produced commercially in the.liquid or solid form. substantially or entirely without the use of purchased power.

Until quite recently, the standard practice in substantially all commercial plants producing carbon dioxide has been to burn coke in a furnace having a boiler associated therewith, whereby gaseous products of combustion are produced. The steam so produced is used to drive an engine which, in turn, operates certain pumps and other mechanism. The gaseous products of combustion are led through scrubbing chambers where the solids and sulphur dioxide are removed, and thence to an absorption tower. The absorption tower, according to standard practice, comprises a column filled usually with coke; and an aqueous solution of sodium carbonate, or other suitable solvent, is caused to trickle downwardly through the mass of coke while the gaseous mixture is caused to flow upwardly through that mass;

whereby a large part of the carbon dioxide in the mixture is absorbed in the so-called lye solution, and the residual gases are permitted to pass out of the absorbing tower.

The liquid which reaches the absorption tower is called, in the art, strong lye; and is a solution of mixed sodium carbonate and sodium bicarbonate. That is, the carbon dioxide which has been absorbed from the gaseous mixture has actually entered into chemical combination with sodium carbonate to form sodium bicarbonate. That solution is led to a boiler which, according to standard practice, is heated by steam exhausted from the above-mentioned engine. As the temperature of the solution rises, the sodium bicarbonate in the solution is broken down to sodium carbonate, with a consequent release of the absorbed carbon dioxide. The resulting weak lye solution is led from the boiler back to the absorption tower to absorb more carbon dioxide; while the carbon dioxide driven off in the lye boiler, together with a certain amount of steam unavoidably driven off therewith, is carried to a condenser where the admixed steam is condensed and separated from the carbon dioxide. carbon dioxide is then carried to compressors and coolers to be condensed to liquid form or frozen to solid form.

It is a matter of record that, in most plants commercially operating to produce solid carbon dioxide inaccordance with the above plan, the

bottom I of the- The a corporation of Delaware 1933, Serial No. 686,486

yield of solid carbon dioxide is only from 40 to 50 percent of the amount of gaseous carbon dioxide produced in the furnace. It is also a matter of record that, in a large number of plants tested, the consumption of purchased power ran 5 from 105 to 120 kilowatt hours per thousand pounds of solid carbon dioxide. We have found it possible to increase materially the percentage of yield, and, at the same time, to eliminate the necessity for purchased power. We have found that, in accordance with our invention, no purchased power at all is required in the manufacture of solid carbon dioxide.

To the accomplishment of the above and related objects, our invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that change may be made-in the specific construction illustrated and described, or in the specific steps stated, so long as the scope of the appended claims is not violated.

Fig. 1 is a flow sheet of a plant constructed in accordance with the present invention;

Fig. 2 is a more or less diagrammatic lateral section of a furnace and boiler installation-forming a part of the present invention;

Fig. 3 is a side elevation of a compressor specially designed for use in connection with the present invention;

Fig. 4 is a side elevation of a pre-heater used in association with the furnace of Fig. 2; and

Fig. 5 is a section through an unloader valve used in connection with the compressor of Fig. 3.

Referring more particularly to the drawings, it will be seen that we have illustrated a furnace indicated generally at l0 and comprising a fire box I l with which is associated a boiler indicated generally at l2; said boiler including a superheater 13. A blower I4 forces air under pressure through an inlet 15 to and through a pre-heater l6 and thence through a conduit I! to the fire box ll. Products of combustion from the fire box H flow over the boiler tubes and through a flue l8 to and through the pro-heater through a conduit It! to a first scrubber 20. From the scrubber 2|], the gases flow through a conduit 2| to, and through a second scrubber 22. In the scrubbers 2|] and 22, the mixture of the products of combustion is purged of solids and water solu- 50 ble gases; and the remaining gaseous mixture, materially cooled, is led from the scrubber 22 through a conduit 23 connected to the intake side of a blower. In the blower 24, the ressure of the mixture of gaseous products of "combustion as I6 and thence l is somewhat raised, and such mixture is forced through the conduit 25 to the absorption column 26 at a positive gauge pressure sumcient to force the mixture through the liquid in the tower and to effect the desired absorption.

While we have found that we can satisfactorily use the usual absorption tower such as we have described hereinabove, we prefer to provide a bubble column of a type which is well known but which, so far as we are advised, has never been used in the absorption step in the carbon dioxide art. Such a column comprises a tall, cylindrical chamber having mounted therein a plurality of trays 21 formed with perforations, said perforations being guarded by bubble caps, and the trays and caps being so constructed and associated that each tray carries a burden of liquid, constantly overflowing to the next lower tray, whereby liquid constantly moves downwardly through the column while gas constantly bubbles upwardly through the liquid carried on the trays. In this manner, the gases and liquid are brought into much more intimate contact, whereby the separation of carbon dioxide is much improved over the above-described usual methods.

As is clearly shown in Fig. 1, the gases under pressure-are introduced at the bottom of the colunm 26 through the pipe 25, and said gases bubble upwardly from one to another of the trays 21, being allowed to escape to the atmosphere through the outlet 28 when they have passed the uppermost tray. During the travel of the gases upwardly through the column 26, substantially all of the carbon dioxide is absorbed in the solution carried by the trays, so that the lowermost trays in the column carry a solution which is substantially all sodium bicarbonate. The strong lye solution flows from the bottom of the column 26 through the conduit 29 and the pump 30, and thence through the conduit 3| to and through a heat exchanger 32 where the solution is somewhat warmed. Thence, the solution flows upwardly through the conduit 33 to a plate column 34, entering at a point below the top of said column. As the strong lye trickles downwardly through the plate column 34, it is rapidly heated by the heating coil of the lye boiler 36, whereby carbon dioxide and steam are driven out of the solution. The capacity of the lye boiler and plate column is increased by by-passing a small quantity of the cold strong lye around the exchanger 32 through the conduit 35 to the extreme top of the plate column 34. This cold strong lye is heated in passing through the top plates of the column 34 by the condensation of a large part of the steam driven off in the boiler 36, and which would otherwise be wasted in the condensers wherein the steam is separated from the carbon dioxide.

The mixture of carbon dioxide and steam driven off in the column 34 passes through the conduit 31 to and through a heat exchanger 38, and thence through a conduit 39 to and through a second heat exchanger 4|), and thence through a conduit 4| to a separator 42, wherein the condensed steam is separated from the carbon dioxide. The water separated in the trap or separator 42 flows through the conduit 44 to a pump 45 and thence through the pipe 46 to join the weak lye solution returning from the plate column 34 through the pipe 55.

Of course, the weak lye flowing through the pipe is hot, and that liquid is caused to flow through the heat exchanger 32 to give up a porthe pipe tion of its heat to the cold strong lye flowing through the pipes 3| and 33 to the column 34.

Cooling water is supplied (in a manner later to be described) through a pipe 41 to the heat interchanger 38, said cooling water effecting the first cooling of the carbon dioxide and steam mixture flowing through the conduit 31. From the interchanger 38, that cooling water flows through a pipe 48 to a second heat exchanger 49, and thence through the pipes 50, 5|, and 52 to the scrubbers 20 and 22. After the cooling water has flowed through the scrubbers 20 and 22, it may be discharged to the sewer through the pipes 53 and 54.

The hot weak lye returning from the column 34 and the condensed water returning from the separator 42 are forced by a pump 56 through the pipe 51 to the interchanger 49, being therein cooled to the absorption temperature. The solution flows from the exchanger 49 through the pipe 58 to the top of the bubble column 26.

For reasons which will be discussed hereinafter, we provide a refrigerating system in the present organization. In the illustrated embodiment that refrigerating system takes the form of a commercial vacuum refrigerating system, and is indicated generally at 59.

A tank 60 contains a liquid medium which, in most instances, will be water. A conduit 6| provides open communication between the upper surface of the water in the tank 60 and a chamber 62 which communicates through a venturi 63 with a condenser 64. One or more'high velocity nozzles 65 in the chamber 62 are directed toward the venturi 63. High pressure, superheated steam is conducted through conduits 66 and 61 to the nozzles 65 and is discharged through said nozzles at a very high velocity and under a pressure surficiently high to permit condensation in the condenser 64 wlth water at available temperatures. The steam flowing through the chamber 62 and venturi 63 at high velocities creates, of course, a suction in the conduit 6|. The condensation in the condenser 64 aids in the production of that suction, whereby a relatively high vacuum is drawn in the tank 60. Such vacuum results, of course, in evaporation of water in the tank 60, with a resultant reduction of temperature of the water in said tank. With available water supply at a temperature of 80 to 90 degrees, it is possible, through the use of this vacuum refrigerating system, toobtain temperatures of from 40 to 45 degrees in the tank 60. Water from an available supply is caused to enter the condenser 64 through the pipe 68. After doing its required work in the condenser 68, that cooling water is led through 41 to the exchanger 38, and thence through the pipe 48, the exchanger 49, the pipes 50, 5| and 52, the scrubbers 20 and 22, and the pipes 53 and 54 to the sewer.

The refrigerated water from the tank 60 flows through the conduits 69 and "to a heat exchanger H, and thence through the pipes 12 and 13 to the return pipe 14 and so back to the tank 60 for further cooling. Refrigerated water likewise flows from the tank 60 through the pipes 69, I5 and 16 to an exchanger 11 and thence through the pipes 18, 13 and 14 back to the tank 60.

cylinder 92 of the compressor.

- caused to flow from the interchanger 'conduit 99, and so to the cylinder 93 where the steam exhausted from the engine 82 flows through the pipe 84 to the boiler 36, and thence through the pipe 85 to the inlet side of a pump 86 which returns the condensed steam through the pipe 81 to the boiler I2. The steam condensed in the condenser 04 is forced by' the pump 88' through the pipe 88 to the inlet side of the pump 86, whence it is returned through the pipe 31 to the boiler I2.

The flywheel 83 of the engine 82 is connected to drive the flywheel 89 of a four-cylinder, threestage compressor. This compressor is illustrated diagrammatically in Fig. 1,-and in elevation in Fig. 3. The compressor includes cylinders 90, 9I, 92, and 93 having therein pistons which are connected in tandem to the flywheel 89.

Pure carbon dioxide which has been separated from condensed water in the trap or separator 42 flows through'the pipe 43 to the first stage cylinder 90 of the compressor. In that cylinder, the gas is compressed to a gauge pressure of 60 pounds per square inch, and it flows thence through the pipe v94 to and through a heat interchanger I28 which is cooled by water at available temperature circulating through the pipes I29 and I30. From the interchanger I28, the compressed gas flows through the pipe 'I3I to the interchanger 11 which, as has been explained, is cooled by refrigerated water from the tank 60. From the interchanger 11, the gas flows through the pipe 95 to and through a water separator I38, and thence through a pipe 96 to the second stage In the cylinder 92, the pressure of the gas is raised to approximately 300 pounds per square inch gauge.

From the cylinder 92, the gas flows through the pipe 91 to a heat interchanger I32 which is cooled by water at available temperatures circulating through the pipes I33 and I34. From the interchanger I32, the gas flows through the pipe I35 to the interchanger II which is cooled, as has been explained, by refrigerated water from the tank 60. From the interchanger H, the gas flows through the pipe 98 to and through a water separator I36 and thence, through the pipe 99, to the third stage cylinder 93 of the compressor.

In the third stage cylinder 93, the gas is compressed to the condensing pressure; and the highly compressed gas flows from the cylinder 93 through the pipe I to and through a first heat interchanger IOI which is cooled by water at available temperature flowing through the pipes I02 and I03. From the interchanger IN, the gas flows through pipe I04 to and through a second heat exchanger I05 which is cooled by refrigerated water from the tank 60, flowing through the circuit 89, I98, I05, I01, 13, 14.

If liquid carbon dioxide is to be the end product of the process, the liquid formed in the interchanger I05 is led directly to the filling stand (not shown). whereit is charged into suitable containers. If, however, the process is to be continued to manufacture solid carbon dioxide as the end product, the liquid carbon dioxide is I05 through the pipe I08 to a first evaporation chamber I09. In the chamber I09, the liquid is permitted to evaporate to a pressure substantially equal to the discharge pressure of the cylinder 92, the gas evaporated in the chamber I09 being led through a pipe IIO to mix in the pipe 98 with the cooled gas flowing from the exchanger H and through the water separator I36. A portion of the gas flowing through the pipe IIO is by-passed around the separator I30 through a conduit I31 to the pipes no and n3 but evaporation in chamber der 92 through the line the rate of evaporation in returning gas is again brought to the condensation pressure. The evaporation in the chamber I09, of course reduces the temperature of the liquid in the chamber I09. The cold liquid flows through a pipe III to a second evaporating chamber II2.

In the chamber I I2, the liquid is permitted to evaporate down to a pressure of approximately 100 pounds per square inch gauge. The gas evaporated in the chamber H2 is led through a pipe II 3 to mix with the cold gas flowing from the interchanger ,11 in the pipe 95; and the major portion of the gas flowing through the pipe II3 is caused to pass through the water separator I38 and thence to the pipe 98. A small portion of the gas flowing through the pipe H3 is by-passed around the separator I38 through the conduit I39, and so to the pipe 96. The gas flowing through the pipe I I3 is thence introduced into the cylinder 92 at a pressure of 60 pounds gauge to be recompressed to approximately 300 pounds per square inch gauge.

The purpose of introducing cold gas from the to mix with the gas in the pipes 95 and 98 is to reduce the temperature of the gas flowing through the pipes 95 and 98 to a point sufficient to effect a suitable separation of water vapor which is present in the gas flowing through the pipes 95 and 98. The by-passes I31 and I39 are so designed and manipulated as to permit just enough cold gas to mix with the warmer gas in advance of the separators I38 and I38 to effect such separation.

The evaporation of liquid in the chamber II2 reduces the temperature of the remaining liquid to approximately minus 50 de e Liquid is permitted to flow from the chamber II 2 through the pipe II I into the ice press H5. The pressure in the chamber H5 is permitted to build up rapidly to approximately 60 pounds per square inch gauge, and thereafter the line H8 is opened to permit gas to flow from chamber II5 through cylinder 9I to cylinder 92, whereby such gas is recompressed in cylinder 92 and returned to the system. When sufficient liquid has entered the chamber I I5 to make a block of solid carbon dioxide of the desired size, communication between the chambers H2 and H5 is closed,

II5 continues, without reduction of pressure in such chamber until the direct freezing of the liquid in chamber H5 is substantially completed; the gas resulting from such evaporation being drawn by the cylin- IIB and cylinder 9|, recompressed in cylinder 92, and so reintroduced into the system. As'a result of this operation, the chamber H5 is relatively slow, and the reduction of temperature due to the evaporation results indirect freezing of the carbon dioxide from the liquid phase to the solid phase, as distinguished from precipitation of solid carbon dioxide in the usual 3 loaded, so that no work is done in the cylinder .be moved to the 9|. When, after the freezing in chamber H5 is practically completed, the pressure in said chamber begins to drop and reaches a value between 40 and 50 pounds gauge, the suction valve at one end of cylinder 9| is released, and that end of said cylinder begins to work; supplying gas to the cylinder 92 at a pressure of 60 pounds gauge. Operation of cylinders 9| and 92 rapidly reduces the pressure in chamber I I5 thereafter and when such pressure drops to a value of about 20 pounds gauge, the other suction valve of cyl- .inder 9I is released and the cylinder 9| comes into full operation. Such operation is continued until the pressure in chamber II5 drops to substantially atmospheric value, whereupon, both suction valves of cylinder 9| are again unloaded to prevent cylinder 9| from pumping the pressure in chamber I I5 to a value below atmosphere.

In Fig. 5, we have illustrated in detail one of the inlet valves for the cylinder 9|.

The wall of said cylinder is formed with a port I40 in which is mounted a grating-MI provided with spaced bars I42 which are concave on their upper surfaces. A second grating I43 is supported upon the grating MI and is provided with apertures I44 staggered with respect to the apertures between the spaced bars. Spring leaves I45 normally close the apertures I44, but-may positions illustrated in Fig. 5 by the fingers I46 of a fork I4'I slidable on bolts I48 connecting the gratings MI and I43 with a housing I49.

The gratings MI and I43 are interposed be- I tween the interior of the cylinder 9| and the interior of the conduit H6.

The fork I41 is provided with a stem I50 which extends into the interior of the housing I49 and is provided therein with a head I 5|. A spring I52 urges said head I5I to its uppermost position. A conduit I53 leads from a source of fluid under pressure to the interior of the housing I49. Obviously, the fork I4! is normally in its uppermost position, being urged thereto by the spring I52. When pressure is admitted to the housing I49 through the conduit I53, the head I5I is depressed, carrying with it the fork I41, whereby the fingers I46 are projected through the apertures I44 to depress the leaves I45 to the positions illustrated in Fig. 5, whereby communication is established between the conduit I I 6 and the cylinder 9|. Obviously any other type of unloading valve might be used in place of that herein illustrated.

It will be obvious that the ideal plant for the production of solid carbon dioxide is one which (a) may be locatednear the market for solid carbon dioxide; (b) may be ofthe desired size without considerations for other,products; (0)

.may be operated when the major product is desired; (d) can use a cheap fuel such as coal; (e) can operate without purchased power; and

- (f) is substantially independent of the temperature of cooling water available at the desired site. Obviously, a plant built primarily for the production of solid or liquid carbon dioxide can readily be designed and located to comply with the first three of the above desiderata.

In our experience, however, no commercial plant prior to our present invention has ever possessed the last three of the above-listed desired characteristics.

All commercial installations known to us use coke as a. fuel. The substitution of coal for coke requires that the volatiles which are present in coal must be burned completely. If combustion is complete, the products of the volatiles are carbon dioxide, water, and sulphur dioxides; whereas if combustion is incomplete they will be carbon dioxide, carbon monoxide, water, sulphur dioxide, hydrogen sulphide, and some complex hydro-carbons. In addition, of course, there is nitrogen which is introduced with'the oxygen in the air.

The scrubbers normally used in this general type of carbon dioxide plant will remove sulphur air, but this has the big disadvantage of diluting.

the final percentage of carbon dioxide present in the flue gas. Such a dilution would tremendously reduce the efficiency of the adsorption step, and would further result in the needless utilization of large amounts of power to handle the increased volume of flue gas.

Using only a small amount of excess air, combustion can be completed if the rate of reaction is high and if time enough is allowed before chilling the flue gas. Of course, further combustion cannot be expected after the flue gases come into contact with the first of the boiler tubes.

In accordance with our invention, the boiler installation illustrated in Fig. 2 is designed to aid in approaching very close to absolutely complete combustion of coal. An under feed stoker H8 of well known type is fed by stoker mechanism II9 driven by a variable speed transmission I20 preferably automatically controlled. The air for supporting combustion is pre-heated as it flows through the pre-heater I6, thereby accomplishing the double objective of reducing the temperature of the flue gases before they are introduced into the scrubbers, and increasing the temperature 'of the air supplied to the furnace grate. Obviously, this increase in temperature of the air supplied to the furnace will result in an increase in the temperature within the combustion chamber II, whereby the ease of reaction is raised to assist in efiecting complete combustion.

In order to extend the time before the gases within the chamber II come into contact with the relatively cold boiler tubes, we build the bridge wall I2I considerably higher than usual; and we cover the bottom row of boiler tubes with a refractory wall I22 extending from the front of the boiler substantially to, or even beyond, the bridge wall I2I. We thus eliminate any bare tubes looking at the fire. We use a high bridge wall and thick, uncooled side Walls. We use a high boiler setting, giving us a large combustion space and a low heat release.

This construction results in the attainment of amount needed by the lye boiler. Any deficiency watch leflctlvh- T high bridge wall assists in mainmore during the summer. It is for that reason taining this condition, and in addition reduces th t ha provided the refrigerating system the area of the n s I. wh r by a tur ulence hereinabove described. If, during the winter in the flue gas before it contacts the boiler tubes months, the refrigerating system is not needed 5 i r t d u h tur ul n e is also du v because of the low temperature of available 5 to complete combustion. natural cooling water, the gas may be by-passed The use of a stoker with a small amount of around the inter-changer so through the pipe' forced draft results in the introduction 'of green 39'; and all of the other heat exchangers, illuscoal in uniform small quantities, so that the trated s being cooled by wat r from the tank amount of volatile matter is introduced to the on, may be cooled by naturally available water-. combusti n cham r u i r y. W consider It should be noted that the use of water in the that an under-feed stoker is desirable, since that scrubbers 2n d 22 which has been warmed by p of Stoker r n s the fines n he M "P passage through the condenser 84, the exchanger t r u h h fuel whereby y are dlfltilled 40. and the exchanger 48, is advantageous; since Oil and l before they can be carrled'out of the higher the temperature of water used in the 15 the furnace y the ue gases unburned or Darscrubbers Ill and 22, the less carbon dioxide will tially burned. be dissolved therein in the scrubbers;

ul s l". d are Suitably introduced The increased efficiency of the plant illustrated in o th l r setup to v d r proper fl w herein, as compared with previously known of the gas s through the boiler tubes. A by-. plants for the production of liquid andsolid car- :0 ba 2 nd the pr h r i p d o h bon dioxide, is due to the following features of if desired, air can be introduced to the furnace th h i -disclo ed plant: at lower temperatures. (a) The use of coal instead of coke as the Wit he l st ed Construction. nd with source of'carbon dioxide, whereby the cost of fuel as careful control f he m ry and secondary per pound of carbon dioxide is reduced. s, air, itis possible to operate with a small amount ob) The use of specially designed furnace and of excess air to obtain a flue gas mixture havboiler equipment whereby complete combustion ing a carbon dioxide content of at least 16 per of the fuel used is attained. cnt- 'With p p Drovliilon 88h removal (c) The production of more steam per dollar. it is possible to maintain this condition without of fuel cost, as the result of using coal instead of an interruption for cleaning fires. coke'and obtaining complete combustion thereof. Of course, the use of coal results in a larger (d) The use of a bubble column in place of production 0! Steam D P d 01 fuel. 11808-1189 the usual coke-filled absorption tower, whereby of the higher heat content of coal. a more perfect separation of carbon dioxide is The steam in the boiler I2 is generated at tt as fair y h h pr u r instance 2 6 pounds p (e) The design of th main engine for drivin qu inch) and is superheated. for instance, the mechanical units of the plant, in such fashion 5 delir efi F. With this superheat nd P as to exhaust almost exactly the amount ofsteam s and h P p Cylinder Volume in thi! main required in the lye boiler, when operatingto drive 40' hil n to permit an a y t fl, it is Possible the various items of mechanical equipment. 40

to Obtain a Water 0! approximate y 20 (I) The use of steam generated in the boiler pounds of steam p r e n il in excess of the requirements of the engine and t back P u at the ns n is maintained the lye boiler, to provide refrigerated water for lit 15 pounds p quare inch. As expla ne cooling the material handled in various steps of hereinbefore, the exhaust steam from the ent process, i gine 82 is-used in the lye boiler II and the coni (g) The use 0 large volumes of relatively densate is returned to the h l f- The Plant is warm water to effect preliminary cooling of the 8 designed t a e amount 0! eXhEult steam material handled before final cooling thereof to c mi from the engine It is Just about e abnormally low temperatures by refrigerated i r on is. of rs m d p with sh p s r Steam (h) The use of a single machine to eirect all from the main bo e T e manure and supernccessary compression in three stages, whereby heat at which the steam is generated is so seth friction losses are cut down. lected that the amou t 01 Steam needed by (i) The use of the particular apparatus and t5 y b01181 Will. in pfll fl thIOlIBh the process herein-described, for refrigerating and 5-1 S d v p enough Power to handle the solidifying the purified carbon dioxide, including c im c ll 1 8 1 h p t ihcllldihlpllmllil. Q the return of portions of evaporated carbon di- BI mp s and Other ms mechanical oxide to the compressing system at relatively high loading. press'urcs. no The largest item in the mechanical load of g (j) The freezing ,1 1m carbon i d 11- oil the plant is the four cylinder c mpre so Th i'cctly from a relatively large body of liquid inhors p w r required for compressing th stead of from the highly divided stream issuing dioxide (both that newly produced and that from a jet, whereby t product is r dense which has been previously compressed and then wand cofigequcntly e tabl as expandcd'for refrigeration) varies with the tem- (lg) The step of pr d-uclngi n carbon dioxo at of the cooling water available If the ide by controlling the evaporation of liquid carnatu a temperature the available "001ml! bon dioxide in such a manner as to hold the preswatcr were de s F r ss, about 25 her sure in the evaporation chamber'substantially cent of. the steam generated in' the boiler II at r bove 60 pounds per square, inch through- Til w u be available either excess D out the period of phase change from liquid to additional blower horsepower to compress the lid,

flue gas to a' higher pressure before introducing We claim asourinventionz the same into the bubble column II; In most 1. A method of solidifying gaseous carbon dilocations, however, naturally available cooling oxide which includes the steps of passing the water will beat a temperature of degrees or gaseous carbon dioxide through a plurality of 75 cumulative compression steps, cooling the compressed carbon dioxide after each compression step, at leastrone of the cooling steps including heat interchange with a relatively large volume of circulating, liquid at substantially atmospheric temperatures followed by heat interchange with an artificially cooled liquid circulating medium, the final cooling step efiecting liquefaction of the carbon dioxide, further cooling the liquefied carbon dioxide by a plurality of cumulative partial evaporation steps conducted in separate chambers, leading the evolved gaseous carbon dioxide from each partial evaporation step into one or another of the compression steps for subsequent final coolinglstep effecting liquefaction of the carbon dioxide, further cooling the liquefied carbon dioxide by a plurality of cumulative partial evaporation steps conducted in separate cham bers, leading the evolved gaseous carbon dioxide from each partial evaporation step through a heat interchange with oncoming fresh gaseous carbon dioxide into one or another of the compression steps for subsequent recompression, and finally freezing the remaining liquid carbon di oxide by controlled partial evaporation at substantially the critical pressure.

3. A method of converting carbon dioxide from its gaseous phase, which includes the steps of refrigerating a body of water by evaporating a portion 'of such body by projecting a jet of high pressure steamacross the surface thereof, bringing a large volume of water at natural temperatures into condensing relation with the mixture of steam and, vapor produced by such evaporation, thereafter cooling a stream of gaseous carbon dioxide by heat exchange with such condensing water, thereafter further cooling such stream of carbon dioxide by heat exchange with a portion of the refrigerated water, compressing the cooled gaseous carbon dioxide to produce therein a pressure in excess of 60'pounds per square inch gage, thereafter absorbing the heat of compression and the latent heat of the gaseous carbon dioxide by bringing a second portion of such refrigerated water into heat exchange relation with the gas, thereby producing a phase change in the gas.

4. A method of producing solid carbon dioxide which comprises the steps of refrigerating a body of water by evaporating a portion of such body by projecting a jet ofhigh pressure steamacross the surface thereof, bringing a large volume of water at natural temperatures into condensing relation with the mixture of steam and vapor produced by such evaporation, thereafter cooling a stream of gaseous carbon dioxide by heat exchange with such condensing water, thereafter further cooling such stream of carbon dioxide by heat exchange with a portion of the refrigerated water, compressing the cooled gaseous carbon dioxide to produce therein a pressure in excess of 60 pounds per square inch gage, thereafter absorbing the heat of compression and the latent heat of the gaseous carbon dioxide by bringing a second portion of such refrigerated water into heat exchange relation with the gas, thereby producing a phase change in the gas, thereafter further cooling the liquid carbon dioxide by partial evaporation thereof, maintaining the pressure upon the liquid carbondioxide at least slightly in excess of 60 pounds per square inch gage, whereby the carbon dioxide is converted directly from the liquid phase to the solid phase, and thereafter reducing the pressure impressed upon the frozen carbon dioxide to atmospheric value.

5.-A method of converting carbon dioxide from its gaseous phase, which includes the steps of passing gaseous carbon dioxide through a series of cumulative compressions, and cooling the carbon dioxide, after each compression step, first by heat exchange at substantially natural temperatures and then by heat exchange with successive charges of an artificially cooled liquid circulating medium, the final cooling step effecting a phase change in the carbon dioxide.

6. The method of producing carbon dioxide in solid form, which includes the steps of burning fuel to produce a mixture of gaseous products of combustion including carbon dioxide, extracting heat from such mixture to raise the temperature of air being supplied to the combustion chamber, compressing such mixture and passing such mixture through a suitable liquid medium whereby a major portion of the carbon dioxide is absorbed in such medium, applying a portion of the heat generated in the combustion chamber to the generation of steam, using at least a portion of the steam so generated to drive an engine, passing such medium enriched with carbon dioxide to a chamber and there heating such medium by. association with the steam exhausted from such engine, to drive carbon dioxide out of such medium, returning the medium stripped of carbon dioxide for contact with further gaseous mixture, cooling such stripped medium during such return by heat exchange with oncoming medium enriched with carbon dioxide, using a portion of the heat generated in the combustion chamber to produce a refrigerating effect upon a suitable circulating refrigerating medium, cooling the gaseous carbondioxide so driven off by heat exchange with water supplied in large quantities from any natural source at temperatures substantially at least as high as the source temperature, subsequently further cooling such gaseous carbon dioxide by heat exchange with said refrigerating medium, using the engine to compress such cooled gaseous carbon dioxide,

= and using one or more further charges of such,

refrigerating medium further to, cool such carbon dioxide, whereby the carbon dioxide is liquefled, evaporating a portion of the liquid carbon dioxide to reduce the temperature of the remaining liquid carbon dioxide, continuously supplying the cold liquid carbon dioxide to a chamber while substantially maintaining a gauge pressure of 60 pounds per square inch in said chamber by further controlled partial evaporation of carbon dioxide in saidchamber, whereby the residual liquidcarbon dioxide so supplied is frozen directly from the liquid phase to the solid phase in said chamber, subsequently reducing the pressure in said chamber substantially to an atmospheric value, .and thereafter compressing the cake of solid carbon dioxide so formed.

7. A method of producing carbon dioxide in solid form, which includes the steps of burning I ing chamber and said furnace and combustion of fuel therein to produce steam, a

fuel under high temperature conditions to effect products of combustion including carbon dioxide.

is produced, compressing such mixture and introducing such compressed mixture to intimate contact with a suitable liquid medium whereby a major portion of the contained carbon dioxide is absorbed in such medium, passing such mediumcnriched with carbon dioxide to anotherchamber and therein heating such enriched mediumto drive off carbon dioxide, utilizing portions of the heat generated upon combustion of such fuel to perform upon the gaseous carbon dioxide a succession of compressing operations and cooling operations, at least one cooling operation, effected by the utilization of such heat, following each of such compressingoperations, whereby said carbon dioxide is liquefied, evaporating a portion of said liquid carbon dioxide whereby the remaining liquid carbon dioxide is further cooled,'and supplying such cold liquid under pressure to a freezthere causing further evaporation while maintaining a pressure in said chamber of approximately pounds per' square inch. gauge, whereby the remaining liquid in said chamber is frozen directly from the liquid phase to the solid phase, thereafter reducing the pressure in said chamber to substantially atmospheric value whereby the temperature of the solid carbon dioxide is reduced, and thereafter compressing the cake of solid carbon dioxide in said chamber.

8. Apparatus for producing solid carbon dioxide, including a furnace, a boiler associated with adapted to be heated by the flue connected with said furnace for conducting certain of the products resulting from the combustion of fuel in said furnace. means -for sepa refrigerating system,

,the compressed carbon arating carbon dioxide from the other components of such products conducted by said flue, said flue discharging into said separating means, a steam engine, means connecting said boiler to supply steam to said engine to operate the same, means for supplying a liquid circulating medium to said refrigerating system, means connecting said boiler to supply steam to said refrigerating system to operate the same-to chili such liquid circulating medium, a multi-stage compressor driven by said engine, connections for leading carbon dioxide from said separating meanstto the initial stage of said compressor wherein said carbon dioxide is compressed, a plurality of heat exchangers, means for leading the compressed carbon dioxide successively through all of the stages of said comwhereby said carbon dioxide is progressively compressed at least to its critical value, dioxide being led, after each compression stage, through one of said heat exchangers, means connecting said refrigerating system with all of said heat exchangers to circulate chilled circulating medium to each of said exchangers to extract heat from the compressed carbon dioxide, whereby the carbon dioxide is liquefied after the final compression stage, other means for further cooling the liquid carbon dioxide, afreezing chamber, means for supplying cold liquid carbon dioxide to said freezing chamber, and means for controlling the rate of evaporation of carbon dioxide in said chamber and for maintaining the pressure in said chamber substantially at the critical point, whereby the liquid carbon dioxide is directly converted to the solid phase.

FRANKLIN B. HUNT.

JABEZ H.. PRA'I'I.

HENRY B. TIRRELL. ROBERT L. TURNER. 

